This invention relates to upflow reactor systems for gas-liquid or gas-liquid-solid feeds. More particularly, this invention relates to upflow reactor systems containing one or more packed beds of contact particles. Upflow ebullated bed reactors have been described in numerous patents and publications. These reactors contain a continuously expanded bed of catalysts or other particules which move randomly throughout the reactor. During operation ebullated beds can be expanded to a volume of 10 to 150% more than the rest volume of the particle bed; see, for example U.S. Pat. No. 4,191,629. Ebullated bed reactors are capable of processing heavy feeds, such as heavy petroleum residua and coal/solid slurries, while providing for low back pressure and continual catalyst replacement. Ebullated bed reactors are particularly attractive for processing solids-containing feeds because the solids can be entrained upwardly through the ebullated bed without causing plugging.
A disadvantage of ebullated bed reactors is that the particle density within the bed is low relative to that of a packed bed. Another disadvantage is that the random motion of materials within the bed causes gross backmixing. Consequently, the concentration of reactants and products becomes essentially uniform within the reactor, thereby resulting in lower reaction rates than are available in packed bed reactors.
One approach to overcoming the disadvantages of ebullating bed reactors is described in U.S. Pat. No. 4,123,348, wherein catalyst particles in an expanded bed are maintained in a continuously pulsating motion achieved by the pulsating addition of one of the reactants to the reaction zone. The continuously pulsating catalyst particles are said to have a greater density of particles than typically achieved in ebullating beds. Gross top-to-bottom vertical backmixing of reactants would nevertheless be obtained in such a process and reaction rates would be lower than obtainable in packed bed reactors.
A process employing a variable feed rate is disclosed in U.S. Pat. No. 2,603,591. Liquid feed is passed into the upper portion of a reactor and gas feed is passed into the lower portion. By manipulation of inlet and outlet valves the feeds are flowed horizontally through a particle bed. U.S. Pat. No. 2,307,434 discloses a downflow reactor with a periodically varying feed pressure. The article "Pulsed-Bed Approach to Fluidization", Kobayashi et al, Chem. Eng. Proc. Sym. Ser., Vol. 66, No. 105 (1970) pp. 47-57 discloses pulsed feed to fluidized beds.